index() method is used to find the position of an element in a list. It searches the list from left to right and returns the index of the first matching occurrence. If the element is not found, it raises a ValueError.

Example: In this example, index() is used to find the position of an element in a list.

a = ["cat", "dog", "tiger"]
print(a.index("dog"))

1

Explanation: a.index("dog") searches for "dog" in the list and element is found at index 1, so 1 is returned.

Syntax

list.index(element, start, end)

Parameters:

• element: The item to search for.
• start (optional): Index from which the search begins.
• end (optional): Index at which the search stops (exclusive).

Return Value: Returns the index of the first matching occurrence and raises ValueError if the element is not found.

Examples

Example 1: In this example, the search is limited to a specific portion of the list using the start and end parameters.

a = [10, 20, 30, 40, 50, 40, 60, 40]
res = a.index(40, 4, 8)
print(res)

5

Explanation: a.index(40, 4, 8) searches for 40 between indices 4 and 7 and first matching value in that range is found at index 5.

Example 2: In this example, the target element appears multiple times. The index() method returns the position of the first occurrence only.

a = ["red", "blue", "green", "blue", "yellow"]
res = a.index("blue")
print(res)

1

Explanation: a.index("blue") returns the index of the first occurrence of "blue" and later occurrences are ignored.

Example 3: In this example, index() is used with a list containing tuple elements.

a = [("Emma", 21), ("Lucas", 22), ("Sophia", 20)]
res = a.index(("Lucas", 22))
print(res)

1

Explanation: a.index(("Lucas", 22)) searches for the exact tuple ("Lucas", 22) and tuple is found at index 1.